There are several metabolic disorders of human and animal metabolism, e.g., hyperglycemia, impaired glucose tolerance, hyperinsulinemia and insulin insensitivity, hyperamylinemia, excess adiposity, and hyperlipidemia. Some or all of the above disorders may occur in the following disease states: non-insulin dependent diabetes mellitus (NIDDM), obesity, hypertension and atherosclerosis.
Hyperglycemia is a condition where the blood glucose level is above the normal level in the fasting state, following ingestion of a meal, or during a provocative diagnostic procedure, e.g., a glucose tolerance test. It can occur in NIDDM as well as obesity. Hyperglycemia can occur without a diagnosis of NIDDM. This condition is called impaired glucose tolerance or a pre-diabetes. Impaired glucose tolerance occurs when the rate of metabolic clearance of glucose from the blood is less than that commonly occurring in the general population after a standard dose of glucose has been orally or parenterally administered. It can occur in NIDDM as well as obesity, pre-diabetes and gestational diabetes.
Hyperinsulinemia is defined as having a blood insulin level that is above normal level in the fasting state, following ingestion of a meal or during a provocative diagnostic procedure. It can be seen in NIDDM or obesity and can be associated with or causal in hypertension or atherosclerosis. Hyperinsulinemia can occur without a diagnosis of diabetes. It may occur prior to the onset of NIDDM. Insulin insensitivity, also called insulin resistance, occurs when the insulin-dependent glucose clearance rate is less than that commonly occurring in the general population during diagnostic procedures such as a hyperinsulinemic clamp See, e.g., DeFronzo, R. A. et al., Am. J. Physiol. 232:E214-E233, (1979)! or a minimal model test. See, e.g., Bergman, R. N. et al., J. Clin. Invest. 68:1456-1467 (1981). Insulin insensitivity is considered also to occur when the blood glucose concentration is higher than that commonly occurring in the general population after intravenous administration of insulin (insulin tolerance test) or when the ratio of serum insulin-to-glucose concentration is higher than that commonly occurring in the general population after a 10-16 hour fast. Insulin insensitivity may be found in NIDDM or obesity and can also be associated with or causal to hypertension or atherosclerosis.
Hyperamylinemia is defined as having an abnormally high blood amylin level. Amylin is also known as diabetes associated peptide (DAP) and insulinoma associated polypeptide (IAP). Hyperamylinemia can be seen in NIDDM or obesity.
Excess adiposity can be seen in NIDDM associated with obesity as well as obesity without NIDDM. It is defined as a higher fat body mass-to-lean body mass ratio than that commonly occurring in the general population as measured by whole body specific gravity or other generally accepted means.
Hyperlipidemia is defined as having an abnormal level of lipids in the blood. Hyperlipidemia exists when the serum concentration of total cholesterol or total triglycerides or the serum concentration of LDL-cholesterol/HDL-cholesterol is higher than that commonly occurring in the general population. It can be seen in NIDDM or atherosclerosis.
The above disease states could be treated by either ameliorating or preventing the metabolic and biochemical disorders. In addition, humans and animals, which have not been diagnosed as having one of the above disease states but evidencing some or all of the disorders described above, could be benefitted by preventing the development of a currently recognized disease state. Therefore, a compound that is useful in the treatment of hyperglycemia, impaired glucose tolerance, hyperinsulinemia, insulin insensitivity, hyperamylinemia, excess adiposity or hyperlipidemia could also be used to treat or prevent NIDDM, obesity, hypertension or atherosclerosis.
3-Guanidinopropionic acid (3-GPA) is an endogenous metabolite found in animals and humans. See, e.g., Hiraga, Y. et al., J. Chromatography 342:269-275 (1985) and Watanabe, Y. et al., Guanidines, edited by Mori et al., Plenum, N.Y., pp. 49-58 (1983). The compound, which is available from Sigma Chemical Co., has been used extensively in the study of creatine metabolism See, e.g., Walker, J. B., Adv. Enzymol. 50:177-242 (1979)! and gamma-aminobutyric acid receptor function. See, e.g., Bowery, R. et al., Br. J. Pharmacol. 50:205-218 (1974). Except as noted below, these studies do not relate to 3-GPA's utility in treating human or animal disease.
Guanidine, monoguanidine and diguanidine compounds have been shown to produce hypoglycemia. See, e.g., Watanabe, C., J. Biol. Chem. 33:253-265 (1918); Bischoff, F. et al., Guanidine structure and hypoglycemia 81:325-349 (1929). However, these compounds were observed to be toxic. In 1957, biguanide derivatives, e.g. phenformin and metformin, were used clinically as anti-diabetic agents. Some members of this class continue to be used today while others have been withdrawn from the market or banned in the United States and most Western countries. See, e.g., Schafer, G., Diabete Metabol. (Paris) 9:148-163 (1983).
Gamma-guanidinobutyramide also known as Tyformin, and the HCl salt of Tyformin, known as Augmentin, were investigated as potential anti-diabetic agents from the mid-1960's until the mid-1970's. While Augmentin produced hypoglycemia, it was reported to produce hypertension in dogs See, e.g., Malaisse, W. et al., Horm. Metab. Res. 1:258-265 (1969)! and respiratory and circulatory collapse in rats and rabbits. See, e.g., Buckle, A. et al., Horm. Metab. Res. 3:76-81 (1971). The free acid of the amide was said to lack hypoglycemic activity See, e.g., Beeson, M. et al., Horm. Metab. Res. 3:188-192 (1971)!.
British patent 1,153,424 discloses the use of certain esters and amides of guanidinoaliphatic acids in the treatment of diabetes mellitus where hyperuremia is present. The patent does not disclose that these compounds have an effect on hyperglycemia or any other symptom or pathological state related to diabetes. In Canadian patent, 891509, the use of esters and amides of guanidinoaliphatic acids were disclosed for treating hyperuremia and hyperglycemia in diabetes mellitus. As noted above, the biologic activity of a guanidino alkanoic acid was known to be different and less favorable so as to be ineffective compared to its amide for treating hyperglycemia.
British patent, 1,195,199 discloses the use of guanidino alkanoic acids or their amides or esters in an insulin-containing, parenterally-administered composition for the treatment of hyperglycemia occurring in diabetes mellitus of the type where the pancreas produces insufficient insulin. According to this patent, the combining of a guanidino alkanoic acid, amide or ester with insulin reduces the risk of hypoglycemia as compared to insulin alone. British patent 1,195,200 discloses the use of guanidino alkanoic acids in a composition containing a guanidino alkanoic acid amide or ester derivative for the treatment of hyperglycemia occurring in diabetes mellitus of the type where the pancreas produces insufficient insulin. The subsequent British patent 1,552,179 discloses the use of guanidino alkanoic acids, their salts, amides or esters in combination with a gluconeogenesis inhibitor for treating hyperglycemic conditions, such as in the type of diabetes mellitus described above. Metformin was cited as an inhibitor of gluconeogenesis. Biological data indicated that HL 523, the preferred guanidino alkanoic acid derivative, was inactive as a single agent in six of seven experiments where blood glucose concentration was measured in alloxan diabetic mice and only weakly active in the seventh study.
Tables 5, 6 and 8 of the '179 patent disclose data which show that no straight chained guanidinoalkanoic acids were active when tested for hypoglycemic activity in alloxan diabetic mice. (Compounds which produced a significant change in blood glucose are denoted by asterisks (*) in these tables.) In Table 5, compound HL 6450 (4-guanidinobutyric acid) was inactive when administered alone. In Table 6, compounds HL 6416 (guanidinovaleric acid), HL 6450 (4-guanidinobutyric acid), HL 6439 (5-guanidinovaleric acid) and HL 6361 were inactive when administered alone. In Table 8, compound HL 6450 (4-guanidinobutyric acid) was slightly active at 2 hours and inactive at 4 hours. However, this slight activity contradicts the findings in Tables 5 and 6. These data showing inactivity of guanidinoalkanoic acids as single agents for lowering blood glucose concentration are supported by the assertion of Beecham Research Laboratories' agents that while 4-guanidinobutyramide "when given to animals in high doses (600 mg/kg sucutaneously in rats) it is hypoglycemic; the free acid (HL 521) lacks this property." (M. F. Beeson et al., (1971) "E.H.: Studies on the metabolism of gamma-guanidinobutyric acid (HL 521) and its amide (HL 523)" Horm. Metab. Res. 3: 188-192.)
The British patents '199, '200 and '179 do not claim utility for guanidino alkanoic acids, as the sole active component, in compositions for treating hyperglycemic symptoms in diabetes. As described above, among the guanidino alkanoic acids tested, several were inactive as a single agent. Thus, a variety of guanidino alkanoic acids lack significant anti-diabetic activity and combination of these compounds with an agent of known anti-diabetic activity, e.g., metformin, is necessary to show beneficial activity.
Furthermore, these patents do not disclose the use of 3-guanidinopropionic acid (3-GPA) to prevent or treat iatrogenic obesity or any other form of obesity. Also, these patents provide no teaching or suggestion of a food product containing 3-GPA.
Aynsley-Green and Alberti injected rats intravenously with 3-GPA, arginine, guanidine, 4-guanidinobutyramide, and 4-guanidinobutyric acid. Arginine and 3-GPA stimulated insulin secretion transiently, but did not affect the blood glucose concentration while the other compounds stimulated insulin secretion but produced a rise in blood glucose concentration. See, e.g., Aynsley-Green, A. et al., Horm. Metab. Res. 6:115-120 (1974). Blachier, et al., observed that 10 mM 3-GPA stimulated insulin secretion by isolated rat islets in vitro. See, e.g., Blachier, F. et al., Endocrinology 124:134-141 (1989). The insulin response induced by 3-GPA was 55% of that occurring when arginine was tested at the same concentration. In rats fed a diet supplemented with 10 mg/g 3-GPA for 30-60 days, the heart glycogen content was increased. See, e.g., Roberts, J. et al., Am. J. Physiol. 243:H911-H916 (1982). Similarly, skeletal muscle glycogen content was increased in rats fed chow supplemented with 10 mg/g of 3-GPA for 6-10 weeks. Mice fed a diet supplemented with 3-GPA at 20 mg/g and supplied with drinking water containing 5 mg/ml 3-GPA for 7-12 weeks had serum glucose concentrations that did not differ significantly from mice receiving unsupplemented chow and water. See, e.g.,:Moerland, T. et al., Am. J. Physiol. 257:C810-C816 (1989).
With respect to adiposity, it is known that in some, but not all cases See, e.g., Shoubridge, E. et al., Biochem. J. 232:125-131 (1985)!, supplementation of the diet with 10-20 mg/g 3GPA results in decreased body weight. See, e.g., Moerland, supra and Mahanna, D. et. al., Exper. Neurol. 68:114-121 (1980). This effect has been attributed to decreased skeletal muscle mass and has not been attributed to reduced adiposity or decreased lipid storage. See, e.g., Mahanna, supra and Shields, R. et al., Lab. Invest. 33:151-158 (1975); and Otten et al.: Thyrotoxic Myopathy in Mice: Accentuation by a Creatine Transport Inhibitor. Metabolism. Vol. 35, No. 6, (pages 481-484, 1986).
Therefore, what is needed in the art is a therapy that may be used in combination with anti-diabetic drugs to treat or prevent obesity, resulting from treatment with an insulin sensitizing drug or an insulin secretion stimulating drug.
Also, patients suffering from any of the above metabolic disorders often experience lack of stamina and endurance and decreased exercise capacity. Other diseases that may result in decreased exercise ability include: diseases resulting from muscular dysfunction, such as post-poliomyelitis chronic muscle fatigue syndrome or muscular dystrophy; diseases resulting from chronic muscular weakness associated with advanced age or chronic immobilization; diseases resulting from tissue hypoxia, such as peripheral claudication, angina, myocardial infarction, and stroke; and wasting diseases, such as cancer. Therefore, what is also needed in the art is a therapy that increases endurance, stamina and exercise capacity in patients who are performing at less than optimal levels.